Bug.
I assembled the helicopter. My coordinates:
-750, 33, -560
I climbed into the helicopter. And ended up in another place. Сoordinates:
-347, 33, -358
I didn't do anything. And in a moment I fell out of the helicopter. Again -750, 33, -560.

Adjust the algorithm respawn. I added mobf mod after the world was created. Now the animals appear only in the new territories. There is no animal on the old areas that were created before adding the mod.